The present invention relates to the measurement of fluid flow volumes and also to methods particularly suited to the monitoring of automotive fuel consumption and more specifically to a miles per gallon meter.
Measurement of fuel consumption has always been a direct way of determining the efficiency of an automobile. Calibrated fuel reservoirs are used for test and tune up purposes and it is becoming more common for the average driver to record his mileage and perform the simple calculation of miles per gallon each time he fills his tank. These averaging methods are useful but do not indicate fuel consumption during normal driving.
Today with rising fuel costs and energy conservation becoming matters of widespread concern, instantaneous fuel consumption monitoring is becoming a most desirable way of saving gasoline by improving driving habits, selecting the best fuel and maintaining the overall efficiency of the vehicle.
The present invention offers a novel simple method for monitoring the miles per gallon fuel consumption of an automobile by injection of air or other gas bubbles into the fuel line, proportional to transversed mileage, generating signals from the air bubbles and processing the signals to provide a read-out in miles per gallon.
This inventor's first experience with air bubble injection came while working with analytical chemistry techniques by which air bubbles are injected into small flow streams for the purpose of separation of solutions to prevent mixing and contamination.
Earlier work has been done on gas flow rate measurement, by photo-optical detection of bubbles of the gas rising in a static fluid. Shields, U.S. Pat. No. 2,967,450, entitled "Optical Bubble Flowmeter," employs a photocell for detection coupled with an amplified and an electronic rate counter (col. 1, lines 29-38).
Air or an immiscible fluid (e.g. mercury) has been injected into a flowing stream for measuring of fluid flow rates. In these devices a signal from the injected substance is electronically detected, and processed with the aid of a timing circuit or counter to provide a conversion to flow rate. Mileage is not introduced.
Ford, U.S. Pat. No. 3,308,660, "High Pressure Flowmeter," describes a flowmeter for measuring flow rate (col. 1, lines 15-17) wherein a drop of immiscible fluid (e.g. mercury) (col. 1, line 26 and col. 1, line 45) is injected at spaced time intervals (col. 1, line 37); two electrode detectors are used (col. 1, lines 41-44) to activate a counter (col. 1, lines 51-52).
Versaci., U.S. Pat. No. 3,403,555, measures the rate of flow of an injected air bubble past two photoelectric detectors (col. 2, lines 27-32). The bubble is injected by the operator when a reading is desired (col. 3, lines 52-55) and a complex timing unit is employed (FIG. 4 and col. 2, lines 27-32).
Gildner, U.S. Pat. No. 3,693,436, "Liquid Flow Meter," utilizes an air bubble of predetermined size injected by means of an air supply tank and valve (col. 4, lines 20-23) as an improved means of measuring liquid flow rate (col. 1, lines 4-16). Two photo-optical detectors (col. 1, lines 34-39; col. 3, lines 10-16) and a timing means, (col. 1, lines 39-41) are used.
Air injection has also been used as a means for separation of a flowing stream into equal volume segments.
Soderkvist, U.S. Pat. No. 3,621,715, "System for Measuring the Flow Volume of a Liquid Flow," discloses a device to introduce exact liquid volumes into test tubes (col. 1, lines 54-58). It uses gas bubbles generated by a gas pump controlled by a logic circuit (col. 1, line 18; col. 6, lines 42-43). A means is also provided for a signal from a detector to control the gas pump injection volume (col. 3, lines 21-23). This system employs its own constant duration air injection control signal. This is a volume separation device and no mileage relationship is involved.
The above-mentioned prior art does not disclose a device for indicating miles per gallon.
A very early proposal for a miles per gallon meter was made by Little in U.S. Pat. No. 2,295,586. Insofar as understood, within a transparent tube coupled into the fuel line, air bubbles produced at arbitrarily timed intervals by a pump, are introduced into the flowing fuel and are visually compared with the linear speed of the surface of an internal helix driven by the speedometer shaft. In at least one embodiment, the helix is adjustable in pitch and is provided with a calibration in miles per gallon such that a visual reading can be taken when the linear velocities of the bubbles and the helix are made equal (col. 1, line 17 to col. 2, line 10). This is the only miles per gallon meter found which proposes the use of air bubbles. The device greatly differs from the present invention. It is a manually operated visual device; the air bubble injector is not governed by the vehicle mileage; and the mileage input is achieved by an independently driven helical member.
Another miles per gallon meter was proposed by Veach, U.S. Pat. No. 3,246,508. Flow rate, e.g. gallons per hour, are determined with the aid of, e.g. an orifice flow meter, and is utilized to control the position of a line pointer on a dial calibrated so that numerous miles per gallon rates are indicated for each position of the line pointer. The dial also has indicia for miles per hour so that the correct value for gallons per mile can be selected by a visual correlation. (col. 1, lines 43-51; col. 1, lines 36-39; col. 6, lines 45-53).
In the search for miles per gallons meters, the three proposals discussed below were found to represent the most recent developments in the art. All three are based on the same fundamental principle. In each, vehicle speed and fuel flow rate are separately evaluated and then these two measurements are combined, electronically processed, and miles per gallon is displayed.
In operation the speed is converted to voltage by a generator coupled with the speedometer cable drive; the flow rate is converted to electrical resistance by a flow transducer; and the read-out is by means of ammeter. The analog equations are, ##EQU1##
The primary problem in these devices is the complexity and reliability of the flow transducer.
In Sorenson, U.S. Pat. No. 3,253,459, the flow rate transducer is a flow activated float device coupled to variable resistor mechanism which may be any of a variety of types as shown in FIGS. 6 to 10 and FIGS. 18 to 22. The transducer is coupled with a voltage generator and ammeter (col. 6, lines 2-4).
Spacek, U.S. Pat. No. 3,673,863 describes a device which is presently being marketed by "Space Kom Inc., " Golela, Cal. 93017. In this device the flow transducer is a photo-optical unit whereby a free standing opaque body is caused by the fuel flow to effect an output signal change of a light sensitive detector (col. 2, line 70 to col. 3, line 2). This resistance value is coupled with the output voltage of a speed transducer, (col. 2, lines 21-31) to control the ammeter read-out, (col. 3, lines 2-4). It is to be noted that the change in resistance is not linear to the change in flow so that a complex linearizing mask must be used in the optical path (col. 5, lines 7-24).
Finally, Taylor, U.S. Pat. No. 3,776,036 discloses a device in which the flow transducer is similar to that of Spacek. The mileage transducer is mentioned but not defined. This device is presently being marketed by Aviatric Ltd., Hampshire, England. The photo-optical flow transducer employs a spring loaded instream opaque float such that the device is not position sensitive (col. 2, lines 7-13). In Spacek the float displacement axis must be kept vertical. An additional feature is the use of a mirror and second photocell to achieve light output balance which may be required due to a change in opacity of the fuel (col 2, line 64, to col. 3, line 6). This is a conventional biasing technique.